Merge pull request #5969 from edolstra/curpos-fix

Fix parsing of variable names that are a prefix of '__curPos'

src/libexpr/nixexpr.cc

@@ -191,7 +191,7 @@ void ExprConcatStrings::show(std::ostream & str) const
     str << "(";
     for (auto & i : *es) {
         if (first) first = false; else str << " + ";
-        str << i.second;
+        str << *i.second;
     }
     str << ")";
 }

src/libexpr/parser.y

@@ -404,7 +404,8 @@ expr_select
 
 expr_simple
   : ID {
-      if (strncmp($1.p, "__curPos", $1.l) == 0)
+      std::string_view s = "__curPos";
+      if (strncmp($1.p, s.data(), s.size()) == 0)
           $$ = new ExprPos(CUR_POS);
       else
           $$ = new ExprVar(CUR_POS, data->symbols.create($1));

tests/lang/eval-okay-regression-20220122.exp

@@ -0,0 +1 @@
+3

tests/lang/eval-okay-regression-20220122.nix

@@ -0,0 +1 @@
+((_: _) 1) + ((__: __) 2)

tests/user-envs.nix

@@ -9,7 +9,8 @@ assert foo == "foo";
 let
 
   makeDrv = name: progName: (mkDerivation {
-    inherit name progName system;
+    name = assert progName != "fail"; name;
+    inherit progName system;
     builder = ./user-envs.builder.sh;
   } // {
     meta = {
@@ -26,4 +27,5 @@ in
     (makeDrv "foo-2.0" "foo")
     (makeDrv "bar-0.1.1" "bar")
     (makeDrv "foo-0.1" "foo" // { meta.priority = 10; })
+    (makeDrv "fail-0.1" "fail")
   ]